The present invention relates to digital broadcasting. Recently, research for appliances capable of transmitting audio broadcasts, video broadcasts, data broadcasts, etc. in accordance with a digital scheme other than an analog scheme, and appliances capable of transmitting and displaying the transmitted broadcasts have been actively conducted. Currently, several appliances are commercially available.
The broadcasting scheme for transmitting audio broadcasts, video broadcasts, data broadcasts, etc. in accordance with a digital scheme is generically called digital broadcasting.
Examples of digital broadcasting are digital audio broadcasting and digital multimedia broadcasting. Such digital broadcasting has various advantages. For example, the digital broadcasting can inexpensively provide diverse multimedia information services, and can be used for mobile broadcasting in accordance with an appropriate frequency band allocation. Also, it is possible to create new earning sources, and to provide new vital power to the receiver markets, and thus, to obtain vast industrial effects.
In conventional digital audio broadcasting, it is possible to transmit audio services, for example, seven audio services, in a frequency band of about 1.5 MHz. All the seven audio services are transmitted in a state of being compressed in accordance with a “Masking pattern adapted universal sub-band integrated coding and multiplexing (MUSICAM)” audio coding scheme.
In other conventional digital broadcasting, for example, conventional digital multimedia broadcasting, digital multimedia broadcasting (DMB) and audio services, for example, one DMB service and three audio services, may be transmitted in a frequency band of about 1.5 MHz. In this case, of course, the three audio services are transmitted in a state of being compressed in accordance with the MUSICAM audio coding scheme.
However, conventional methods for transmission of digital broadcasts have the following problems.
First, there is no conventional coding scheme having a compression rate higher than those of recently-developed or practically-used audio compression techniques. For this reason, there is a problem in that the number of audio services transmittable in a limited frequency band is relatively small.
Furthermore, when a broadcast stream compressed using a plurality of different codec scheme is transmitted, conventional cases have a problem in that there is no broadcast receiver capable of decoding the transmitted broadcast stream. This is because the existing broadcast receivers can decode only a broadcast stream compressed in accordance with a single, particular audio codec scheme.
Second, there is a problem in that conventional digital broadcast receivers cannot output an audio signal coded using a plurality of audio coding schemes.
To this date, many techniques associated with signal compression and signal restoration have been proposed. Generally, objects, to which such techniques are applicable, are various data including audio and video data. In particular, signal compression or restoration techniques have been advanced to achieve an enhancement in picture quality or sound quality while achieving an increase in compression rate. Also, many efforts have been made to achieve an enhancement in transmission efficiency, in order to enable the techniques to be suited to various communication environments.
However, it is public opinion that there is still a margin for effective enhancement of transmission efficiency. Accordingly, there is a demand for concrete research for optimization of signal transmission efficiency, even in complex communication environments, through development of a new signal processing scheme.